Multiple-break vacuum-type circuit interrupters



OCt. 8 1968 TO5H|Q |T ETAL 3,405,245

MULTIPLE-BREAK VACUUM-TYPE CIRCUIT INTERRUPTERS 2 Sheets-Sheet .l

Filed May 26, 1965 PRI R ART Fl 62A.

FIGZ.

ATTORNEY Oct. 8, 1968 3,405,245

MULTIPLE-BREAK VACUUM-TYPE CIRCUIT INTERRUPTERS Filed May 26, 1965TOSHIO ITO ET Al- 2 Sheets-Sheet 2 United States Patent() 3,405,245MULTIPLE-BREAK VACUUM-TYPE CIRCUIT INTERRUPTERS Toshio Ito and ToshimotoOhkura, Amagasaki-shi, Japan, assignors to Mitsubishi Denki KabushikiKaisha, Tokyo, Japan, a company of Japan Filed May 26, 1965, Ser. No.458,943 Claims priority, application Japan, May 29, 1964, 39/ 30,197 3Claims. (Cl. ZOU-144) ABSTRACT OF THE DISCLOSURE A multiple-breakvacuum-type circuit interrupter is provided having three separablearcing contacts disposed within an evacuated enclosure. A cylindricalcondensing shield is interposed between the arcing contacts and theouter insulating portions of the evacuated enclosure. A flexiblediaphragm-like supporting plate supports an intermediate arcing contactwhich makes abutting engagement with two outer arcing contacts. One ofthe outer arcing contacts is moved to abut the flexibly mountedintermediate contact and force the latter into and out of contactingengagement with an outer stationary contact. A double-break device withthe intermediate contact at the potential of the oating condensingshield is thus provided.

This invention relates generally to multiple-break vacuum-type circuitinterrupters, and, more particularly, to multiple-break vacuum-typecircuit interrupters having improved contact and shielding structures.

A general object Iof the present invention is to provide an improvedvacuum-type circuit interrupter of the multiple-break type. n

Another object is to provide an improved multiplebreak vacuum-typecircuit interrupter having a condensing shield structure which ispreferably mechanically and electrically connected to an intermediatecontact structure and which is at a oating potential.

Still a further object of lthe present invention is the provision of animproved multiple-break vacuum-type circuit interrupter having `a veryshort opening stroke.

Still a further object of the present invention is the provision of animproved multiple-break vacuum-type circuit interrupter having twovacuum chambers, so that a loss of vacuum in one vacuum chamber will notcause flashover, but the adjacent intact operative vacuum chamber withits own series break will hold the voltage.

Vacuum-type circuit interrupters are generally composed of a vacuumcontainer including an insulating portion'having accommodated thereincontact members, and a shielding member for preventing a metallic vapor,evolved from opening and closing these contact members, from adhereingto the aforesaid insulating portion. A dielectric breakdown voltage fora vacuum gap is approximately proportional to the 0.5th power of thelength of the gap. Even if the length of the gap would increase, thereis little hope of a` great increase in withstand voltage. An increase inthe length of the gap is rather disadvantageous from an economicalstandpoint. For these reasons, the conventional vacuum-type circuitinterrupters have their rating voltages limited to from to 20 kv.

Generally, the vacuum-type circuit interrupter according to the presentinvention comprises a vacuum container including an yinsulating portion,first and second contact members disposed in opposing relationshipwithin the vacuum container with at least one of the contact membersbeing movable, a shielding member at a floating potential mountedintermediate the insulating members to enclose these contact membersthrough a predetermined 3,405,245 Patented Oct. 8, 1968 spacing, and acontact member at a oating potential mounted to the shielding member soas to form a plurality of gaps substantially equal in length between thetwo contact members upon opening. By further interposing the separatecontact member between the contact members to provide a plurality ofgaps, the invention can provide a crucit interrupter having a withstandvoltage which is extremely high, as compared with prior-art vacuum-typecircuit interrupters having the same length of gap. Further, due to itsfloating potential, the contact member which must be mounted to aportion not applied with the potentials of a first and second contactmember, that is, to the insulating portion is mounted to the shieldingmember which should similarly be at the floating potential, and which ismounted to the insulated portion of the vacuum container resulting inimportant advantages, such as extreme .compactness of construction and asimplicity of arrangement.

Further objects and advantages will readily become apparent upon readingthe following specification, taken in conjunction with the drawings, inwhich:

FIGURE 1 is a vertical cross-sectional view taken through aconventional-type circuit interrupter, the contact structure beingillustrated in the open-circuit position;

FIG. 2 is a vertical cross-sectional view taken through a vacuum-typecircuit interrupter embodying principles of the present invention, againthe contact structure being illustrated in the open-circuit position;

FIG. 2A is a somewhat diagrammatic view illustrating how the two movablecontact members of the vacuumtyp circuit interrupter of FIG. 2 may bemechanically operated in unison, the interrupter being shown in theopen-circuit position;

FIG.` 3 is a vertical cross-sectional view taken through a modied-typecircuit interrupter embodying principles of the present invention;

FIG, 4 is a fragmentary view of a pair of cooperating contacts having acertain gap spacing therebetween;

FIG. 5 is a view somewhat similar to FIG. 4, but i1- lustrating the useof an intermediate contact member with a total gap spacing equal to thatof the separation between the contact members of FIG. 4; and,

FIG. 6 is a graph illustrating the relationship between the withstandvoltage and the total gap distance.

Referring to the drawings, and more particularly to FIG. l thereof, thereference numeral 1 generally designates a vacuum-type circutinterrupter of a conventional type. A casing 2 contains a high vacuum.Preferably, the casing 2 includes a cylindrical insulating wall 2 andopposing metallic end portions 3, 4, secured in any suitable manner tothe end extremities of the insulating envelope 2. The reference numeral3- designates an upper enclosure plate forming an upper wall for thevacuum container 2, and the reference numeral 4 designates the lowerclosure end plate for forming the lower wall of 'the vacuum container 2.Preferably, as well understood by those skilled in the art, the endclosure plates 3, 4 are composed of a suitable conductive material, suchfor example, as copper.

Provided centrally through the lower closure end plate 4 is an aperture6, which accommodates the opening and closing movement of a contact rod10. Extending downwardly from the upper end closure plate 3 is astationary contact rod 7, which supports a relatively stationary contact9, as shown. Cooperating with the relatively stationary contact 9 is amovable cooperating Contact 12, which is supported at the upperextremity of the movable contact rod 10. Any suitable operatingmechanism may be provided to elect reciprocal opening and closingmovement of the movable contact rod 10, a bellows 18 being provided tomaintain the vacuum within the container 2.

As shown' in FIG. l, the movable contact rod 10 has` A a radiallyoutwardly-extending ange portion 11, which is secured, as by soldering,to the upper extremity of the bellows 18. The lower end of the bellows18 may be secured by a suitable solder or brazing connection adjacentthe aperture 6 provided in the lower end closure plate 4.

In the open-circuit position of the circuit interrupter 1, asillustrated in FIG. 1, there is provided a gap g, as shown in FIG. 4 ofthe drawings. Additionally, there is provided interiorly of the casing 2a shielding member 14, which is mounted at one end to the stationarycontact rod 7. As shown, the shielding member 14 encloses bothcooperable contact members 9, 12 through a predetermined lateralspacing.

The vacuum-type circuit interrupter 1 of FIG. l, typical of prior-artvacuum-type circuit interrupters, exhibits the relationship between thelength of gap g and the withstand voltage, as shown by curve B in FIG. 6of the drawings. For example, if it is desired to make the dielectricbreakdown voltage equal to 60 kv., the gap distance is necessary to beapproximately mm. in length.

Embodiments of vacuum-type circuit interrupters incorporating theprinciples of the present invention are described below in particularrelationship with FIGS. 2 and 3 of the drawings. With particularreference being had to these iigures, it will be noted that thereference numeral 19 designates a vacuum container maintaining a highvacuum. The reference numeral 20 designates a first insulating portionformed as a cylindrical tube, and the reference numeral 20' designates asecond insulating portion in the form of a cylindrical tube, anddisposed in alignment with the said first insulating portion 20, withboth insulating portions 20, 20 forming a surrounding envelope 19 forthe vacuum-type circuit interrupter 21.

The reference numeral 30 designates an upper end closure plate formingan upper wall for the vacuum-type circuit interrupter 21 and thereference numeral 40 forms a lower wall for the vacuum circuitinterrupter, with both end plates 30 `and 40 preferably being formed ofa conductive metal. Provided through the end closure plate 40 is anaperture 6, which accommodates reciprocal opening and closing movementof a movable contract rod 23. Additionally, FIG. 2 shows a secondmovable contact rod 23' which may be actuated simultaneously with thelower movable contact rod 23 in a manner diagrammatically indicated inFIG. 2A of the drawings.

With reference to FIG. 2A of the drawings, it will be noted that' 'thetwo movable contact rods 23, 23 are pivotally connected, las at 24, 24',to pivotally-mounted operating levers 25, 25' respectively pivoted uponstationary supports 26, 26'. The ends of the two pivotallymountedoperating levers 25, 25 are connected to a toggle device 28 comprising apair of toggle links 28a, 28b pivotally connected by a toggle knee pin28C. The outer extremities of the toggle links 28a, 28b are pivotallyconnected, as at 31, 31', to the left-hand extremities of the operatinglevers 25, 25', as illustrated in FIG. 2A of the drawings.

To eiect leftward closing movement of the knee pin 28C of the toggledevice 28, there is provided, for example, an actuating solenoid 34,which may be energized by the pressing of a suitable close button 35.Also, as will be apparent, the circuit interrupter may be latched in theclosed-circuit position by a latching pin 38, which will latch over acatch 39, and may be released by the energization of a suitable solenoid41 by the closing of an open button 42 connected in circuit with asuitable energizing source, as shown.

From the foregoing description, it will be apparent that upon closingthe close button 35, the solenoid 34 will become energized, causingleftward closing movernent of the toggle links 28a, 28b to effect inwardclosing motion of the contact rods 23, 23. The breaker 21 may be latchedin the closed position, and upon closing the open button 42, thesolenoid 41 will become energized thereby causing a retraction of thelatch rod 38 thereby releasing the solenoid rod 42 as caused by asuitable biasing compression spring 44.

Disposed at the inner extremities of the movable contact rods 23, 23'are movable'contacts 50, 50', which make abutting engagement with" anintermediate third contact 60. In the vacuum-type circuit interrupter 21of FIG. 2, it will be noted thatthe intermediate contact 60 is iixedlysupported upon a metalliepartition plate 61 constituting an inwardextension of the condensing shield structure 62. A radiallyoutwardly-extending plate portion 64 extends outwardly from thecondensing shield 62, and is secured, such as by soldering, to `an outerperipheral envelope plate 66. The plate 66 may, as shown, be suitablysecured to the end extremities of the insulating portions 20, 20.

With the construction illustrated in FIG. 3, the intermediate contact 60is resiliently supported by a exible diaphragm-type supporting plate 80,which is secured to the outer condensing shield structure 62. The latteris supported in a manner similar to that illustrated in FIG. 2 of thedrawings.

In the open-circuit position of the vacuum devices of FIGS. 2 and 3, itwill be noted that the gap spacing g', g is substantially equal to thatof the gap g illustrated in FIG. 4, the multiple-break contactarrangement being illustrated in FIG. 5 of the drawings for comparisonpurposes.

The reason for rendering both gaps g and g" to be substantially equal inlength to each other is that the third contact member 60 be put at apotential equal to an intermediate potential between the potentials ofthe rst and second contact members 50, The tubular shielding member 62for enclosing the contact members 50, 50 through a predetermined spacingmay be, for example, of an insulating material, such as glass, or ametallic material, such `as aluminum. The shielding member 62 is at thesame potential as the third contact member 60.

It will be noted that in the construction set forth in FIG. 2, the thirdcontact member is stationary, whereas in the multiple-break constructionof the device illustrated in FIG. 3, the intermediate contact member 60is resiliently supported and is movable. The third contact member 60,the mounting therefor, and the shielding member 62, together with thismounting are insulated from the first and second contact members 50, 50and are ata floating potential.

The vacuum-type circuit interrupter in accordance with the principles ofthe present invention exhibits the relationship between length of gapand withstand voltage as shown in curve A in FIG. 6 of the drawings. Forexample, if it is desired to make the dielectric breakdown voltage equalto 60 kv., the gap is required to be approximately 1 millimeter inlength. This results in the gaps g' and g being requiredonly to be 0.5millimeter in length respectively.

The operation of the vacuum-type circuit interrupters according to thepresent invention will now be described: Referring rst to the`construction of FIG. 2, there is shown a vacuum-type circuitinterrupter 21 in its open position. To change the interrupter from itsopen position to its closing position, a suitable operating mechanism,described hereinafter, is operated to drive both movable supporting rods23, 23' in an inward direction to move the iirst and second contactmembers 50, 50 inwardly until these two movable contact members engagethe intermediate relatively stationary contact 60. The interruptingoperation is obtained by a reversal of the aforementioned operation.

During the opening operationsuitable mechanism, such as indicated inFIG. 2A of'the drawings, may be provided to provide an outwardv openingmovement of the two movable contact members 50, 50.

With reference to the vacuum-type circuit interrupter 70 of FIG. 3incorporating principles of the present invention, it will be observedthat to move the contacts 50, 50' from their open positions, as shown,to their closedcircuit position, it is necessary to effect upwardclosing movement of the lower movable contact rod 23. This is obtainedby any suitable operating mechanism. In the closing direction, it willbe apparent that when the lower movable contact rod 23, carrying thesecond movable contact 50, engages the intermediate, or third movablecontact 60, it will cause upward closing movement of the latter untilabutment is obtained with the first or relatively stationary contact S'.During the opening 0peration, downward opening movement of the movablecontact rod 23 will permit the resiliency of the flexible supportingdiaphragm 80 to cause downward opening movement of the intermediatecontact 60, and consequent separation between the first and thirdcontact members 50', 60 until the gap distance g is obtained. Continuedopening downward travel of the lower movable intermediate contact rod 23will cause subsequent disengagement between the second movable contactmember 50 and the third intermediate movable contact member 60 resultingin a gap spacing g.

As previously described, vacuum-type circuit inter-A rupters 21, 70according to the present invention comprise the intermediate contactmember 60 at a floating potential disposed between the first and secondcontact members S0, 50' or 50, 50" to result in the formation of firstand second gaps g and g" during the opening operation of substantiallyequal length. The third contact member 60 has an intermediate potentialwith respect to the first and second Contact ymembers 50, 50. Forexample, assuming that the dielectric breakdown voltage has a magnitudeof 60 kv., prior-art-type vacuum circuit interrupters were required toinclude a gap of approximately mm. in length, whereas the circuitinterrupter 21 or 70 of the present invention is only required toinclude a gap spacing of approximately 0.5 mm. in length provided thatthe number of gaps is, for example, two in number. Thus, the inventioncan provide for an extremely high dielectric breakdown voltage withextremely short gaps. Also, since the.vacuum circuit interrupteraccording to the present invention may include a plurality ofindependent gaps with independent vacuum chambers, there results nodisadvantage in that the occurrence of a dielectric breakdown across onegap may cause a short -circuiting of the contact members, as in the caseof a conventional-type circuit interrupter including only a single gap.This results from the fact that if any of the gaps is short-circuitedfor any reason, the other series independent gaps will exist. Further,in order to put the third contact member 60 at a floating potential soas to cause the same to be at an intermediate potential with respect tothe first and second contact members, it must be insulated from the rstand second contact members. However, the shielding member 62 has beenconnected to a portion 66 insulated from the first and second contactmembers 50, 50', and thus put at a floating potential, and theintermediate contact member 60 which is at the lloatinglpotential hasbeen directly connected to this portion. This not only greatly reduces afear of short-circuiting the shielding member 62 with the first andsecond contact members, but also eliminates the necessity for mountingthe shielding member 62 and the contact member 60 at the floatingpotential to separate mounting positions within the vacuum container 19.The result is a compact-type vacuum circuit interrupter.

If the power circuit has been interrupted by a conventional-type vacuumcircuit interrupter, a reverse or residual flows through the same for along period of time after the interruption, the magnitude of the currentreaching the order of approximately 1 ampere. As such a high residualcurrent flows through two interruption points (the gaps g and g seriallyconnected), the division of voltage depended upon the construction isnegligible in the transient state occurring immediately after theinterruption. Also the flow of residual current determines thepotentials of the contact member 60 at the floating potential, and ofthe shielding member 62 and serves to cause such contact and shieldingmembers 60, 62 to be at intermediate potentials in the transientinterruption state.

While the vacuum container 19 may be arranged to be hermetically dividedinto two separate parts 19A, 19B for maintaining its integrity if onepart should lose its vacuum, the performance'of the vacuum circuitinterrupter is not changed regardless of whether or not both sides ofthe mounting for the condensing shield communicates with each other bymeans of holes provided through the supporting plate 61, 80.

Although there have been illustrated and described specific interruptingstructures, it is to be clearly under.

stood that the same were merely for the purpose of illustration, andthat changes and modifications may be readily made therein by thoseskilled in the art without departing from the spirit and scope of theinvention.

We claim as our invention:

1. A vacuum-type circuit interrupter including casing means defining anevacuated envelope, said casing means including two axially-alignedcylindrical -insulating sections (20, 20') with annular metallicsupporting means (66) interposed therebetween, a cylindrical condensingshield structure (62) supported adjacent its mid portion to aradially-outwardly extending portion (64) sealed to said annularsupporting means, a flexible metallic diaphragm sealed to and extendinginwardly from the mid portion of said shield structure and supporting anintermediate contact button (60) at its center, a stationary contactsupported on an end plate of said evacuated casing'means and extendingaxially into one of said cylindrical insulating sections (20) and havinga contact face close `to but spaced from said intermediate contactbutton, a

moving contact movably supported on an opposite end plate of saidevacuated casing means and extending axially into the other cylindricalinsulating section (20') for abutting engagement `with said intermediatecontact button to force the latter into abutment with the contact faceof the stationary contact, said flexible metallic diaphragm and saidoutwardly extending portion of said sealed struct-ure collectivelydefining an impervious partition means constituting part of twocompletely independent evacuated chambers (19A, 19B), whereby the lossof vacuum in one chamber does not affect the evacuated state in theother chamber which itself will hold the impressed voltage in theopen-circuit position of the interrupter.

2. The vacuum-type circuit interrupter of claim 1, wherein thecylindrical condensing shield structure is of metal.

3. The vacuum-type circuit interrupter of claim 1, wherein the flexiblemetallic diaphragm has annular concentric corrugations provided thereinsurrounding the intermediate contact button for providing flexibility.

References Cited UNITED STATES PATENTS 2,326,074 8/ 1943 Slepian 200-1442,863,026 12/1958 Jennings 200--144 3,014,109 12/1961 Burger 200-1443,038,980 6/1962 Lee ZOO-144 3,174,019 3/1965 Jansson 200-144 3,200,2228/ 1965 Hawkins 200-144 FOREIGN PATENTS 607,604 l/ 1935 Germany.

ROBERT S. MACON, Primary Examiner.

